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(11) | EP 0 545 473 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | TCAS II pitch guidance control law and display symbol |
| (57) An airplane pitch guidance control law and display symbol for a Traffic alert and
Collision Avoidance System (TCAS) is disclosed. The control law converts a TCAS computer-generated
vertical air speed command into a pitch guidance command. The pitch guidance command
controls the location of a symbol (51) on the pitch axis of an electronic attitude
display (21) that guides a pilot toward a pitch attitude that will result in a vertical
speed that eliminates a collision threat. The preferred symbol is a pitch axis leg
(53) and a pair of outwardly diverging legs (55a, 55b). The pitch axis leg (53) defines
the minimum climb or descent attitude required to achieve a safe climb or descent
angle. The pitch axis leg (53) and the diverging legs (55a, 55b) combine to define
a climb or descent attitude range to avoid. The distance between the pitch axis leg
53 and the boresight 39 of the airplane symbol of the display is controlled by a RACMD signal produced by: subtractively combining the vertical speed command (VSTCAS) produced by a TCAS II computer and the vertical speed of the airplane (VSIND); multiplying the result by a sensitivity factor K whose value is related to the
true air speed of the airplane and 57.3 to approximate the arc tangent of the quotient;
and subtracting a factor that compensates for the fact that flight path angle changes
lag pitch attitude changes. |